on ye art and mysteries of turning

1. on ye art and mysteries of turning 艺术与车床奥秘 主讲：周燕飞

2. 前言INTRODUCTION 每个人都可以要求自己成为发明家吗？我们人类社会从来就拒绝神话，从与邪恶作斗争的神奇英雄到揭示自然奥秘、改变人类恶劣的生存条件科学界和工业界的英雄的壮举已经证明了这一点。而这些英雄们壮举又被发明者作为新神话来所崇拜，使我们关于技术历史的思想和教育被“第一个是谁”的思想笼罩着。让我用“第一个是什么？”这个更本质的问题来反驳吧。大多数发明是顺序渐进的，不会一出现就羽翼丰满地进入人们的生活。这没有比车床的发展历程更好的例子了。她是机床之母，唯一的通过其本身可以制造出来的机床。通过以下车床发展的图片，我希望表明同样想法可能反复产生，但是，在缺乏想象、技术和应用背景的情况下，一般而言，这些想法只能一次次沉睡，只有这三个因素度满足的情况下这种沉睡才能苏醒。 Can any man lay claim to be the inventor of anything? Our society, robbed of legend during the enlightenment turned instead from mythic heroes who slew dragons to scientific and industrial heroes who unearthed the mysteries of nature and tamed the unruly and precarious conditions of our existence. Part of this new mythology was the cult of the INVENTOR, and much of our thinking and education on the history of technology is clouded by thoughts of "who was the first?" Let me counter this with a question of a more useful nature..."what was the first?" Inventions for the most part evolve, and do not spring into fully fledged life at the touch of godlike geniuses. No better example is there than the Lathe, the queen of machine tools, and the "only self replicating machine tool". In the following series of illustrations, I hope to show that the same ideas are born over and over again, but, because of lack of imagination, lack of technology or lack of application are fated to slumber once more in the collective gestalt until all three factors for their resurgence are met.

3. earliest picture of a lathe From remaining artifacts, it can be shown that the lathe was in existence by 1000 BC. This Egyptian drawing from the 3rd century BC is the earliest known illustration. By 600 B.C., the lathe had been spread by the expansion of Celtic cultures over Europe - reaching from Scotland to the Crimea and from Denmark to Spain. The motive power of this Egyptian lathe is provided by the assistant on the right, but this was soon done away with by the use of a bow with its string wrapped around the work, powered by the operator who used his foot and other hand to steady the cutting tool. The bow lathe is still in use today in India for ivory turning, and amongst watchmakers in the form of the jewellers "turns" for precision work in metal. For the first couple of thousand years, lathe work was necessarily "between centres" work. The use of pointed supports engaging in small holes allows a body to be held rigidly in place without gripping it, and consequently, without distortion and with great accuracy. "The two points - centres - acting together can without exerting any force, effectively prevent translation in any direction, and resist the rotation of the workpiece on the other two axes. Furthermore, provided the points fit the holes in which they are engaged, the work can be removed, and replaced with absolute exactitude - the setting is 'repeatable' and almost perfectly so..."-Tubal Cain, "Workholding in the Lathe", pp9-10 现存的古文物告诉我们，车床在公元前10世纪就已经出现了，这幅公元前三世纪的埃及图画是现今遗留下来关于车床最早的描述。到公元前6世纪，随着凯尔特文化的在欧洲的迅速传播，车床也引入到了整个欧洲，从苏格兰到克里米亚半岛，从丹麦到西班牙。最初，这种埃及车床的动力由图片右边的助手提供，而操作人员用脚和另一只手固定住刀具，但很快这种方法就被一种环绕工件的弓形车床所取代。如今，印度人仍然使用这种弓形车床来切割象牙，由于这种车床加工的精密性,手表制造商也利用它来加工宝石以保证手表时间的精确性。几千年来，车床一直都是人们的工作中心。点固定能使工件保持很好的位置精度，而不需要对工件进行夹持，从而使工件不至于产生扭曲变形而获得很高的加工精度。“两点－中心共同对工件固定，不会产生任何力，从而防止了任何方向的平移运动以及以另外两个轴为中心的旋转运动。此外，通过点与孔的配合，工件可以很精确地装卸，这一装置是可以重复实现的，而且几乎是完美的......"----《车床工装夹具》P9-P10，Tubal Cain left: The earliest picture of a lathe is one on the wall of an Egyptian grave of the third century B.C.（above left）, shown here in a line drawing. The man at left is holding the cutting tool. The man at the right is making the workpiece rotate back and forth by pulling on a cord or thong. 左图：关于车床最早的图片记载是公元前3世纪一个埃及坟墓墙上的图画(坐右图)，这里给出的是一幅素描画。画面中左边的工人正拿着刀具，右边的工人正在拉着一条绳子或皮带使工件来回旋转。

4. bow lathe(1) The Egyptian lathe is based on a stone carving which may be the earliest pictoral representation of a lathe. Artifacts as early as the 7th century B.C. have been found which appear to have marks consistant with having been turned. There is some speculation that the Egyptian lathe may actually represent a horizontal set-up, and that it was been portrayed vertically because artists of the time lacked the knowledge of how to represent their subjects with perspective. Although with enough weight on the upper horitcal board, it may well have worked as portrayed with the worker holding the tool and bracing it against the upright

5. bow lathe(2) A Indian Lathe based on a similar idea as the Egyptian Lathe above 与埃及人的车床相似的印度人的车床 A diagram of a simple Roman-era bow lathe, showing how the head and tail stocks are buried in the ground to hold the set-up steady. 这是一幅罗马时代的弓拉式车床示意图，床头箱和尾架埋在地下以保持机床稳定工作。 Turning Chess piecesfrom Alphonso X's "Book of Games," Circa 1280 A.D. As with the Egyption stone carving it is believed that this was actually a horizontal set-up. There is no tool rest so the turner is steadying his tool between his toes. There are similar simple lathe that are operated in the same manner which can be seen in third world countries to this day. 车削国际象棋，车床实际上是水平安装的，车工用两脚趾夹持刀具，这种车床在第三世界国家还在用。 Turning Backgammon piecesAnother image from Alphonso X's "Book of Games," showing a man turning Backgammon pieces. 这是车削西洋双陆棋的画面

6. bow lathe(3) • Hand-pumped Bow Lathes • A"Turn Bench" from Joseph Moxon's Mechnick Exercises, 1680. • "Small work in Metal is Turned in a Iron Lathe called a Turn -bench... When they use it they screw it in the Chaps of a Vice, and having fitted their Work upon a small Iron Axis, with a Drill Barrel fitted upon a square Shank at the end of the Axis next the left hand, they with a Drill-bow and Drill-string carry it about."-Joseph Moxon's Mechnick Exercises A clockmaker's lathemade of brass and driven by a bow. Scanned from: Country Furniture, by Aldren A Watson. Lyons & Burford, publishers. Watchmaker's Bow Turn & CaseCirca late 1700's. Scanned from "With Hammer in Hand, The Dominy Craftsmen of East Hampton, New York" by Charles Hummel, 1968.

7. bow lathe(4) • Hand-pumped Bow Lathes • A"Turn Bench" from Joseph Moxon's Mechnick Exercises, 1680. • "Small work in Mettal is Turned in a Iron Lathe called a Turn -bench... When they use it they screw it in the Chaps of a Vice, and having fitted their Work upon a small Iron Axis, with a Drill Barrel fitted upon a square Shank at the end of the Axis next the left hand, they with a Drill-bow and Drill-string carry it about."-Joseph Moxon's Mechnick Exercises A clockmaker's lathemade of brass and driven by a bow. Scanned from: Country Furniture, by Aldren A Watson. Lyons & Burford, publishers. Watchmaker's Bow Turn & CaseCirca late 1700's. Scanned from "With Hammer in Hand, The Dominy Craftsmen of East Hampton, New York" by Charles Hummel, 1968.

8. bow lathe(5) Watchmaker's latheA watchmakers turn with elaborate etching decorating it. Scanned from Joseph Moxon's Mechnick Exercises, 1680. My antique watchmaker's, or jeweler's lathe mounted in a tiny bench vice. The centers from my watchmaker's lathe showing the slots cut in the center points.

9. The Pole Lathe（1） While perfectly satisfactory for small work, the bow lathe soon gave way to the pole lathe. This invention was probably developed by the Celts and Etruscans, who were Europe's first master turners. By pressing down on a stirrup or pedal, the work revolves and the spring pole or in some cases, fixed bow is drawn down. The pressure of the foot is released causing the work to spin rapidly and allowing the turner to concentrate on manipulating the cutting tool. The Celts used lathes to turn spokes and axles for their magnificent chariots, bowls, bracelets, wax patterns for cast objects, soft metal and most important of all, grindstones. The Celts and Romans were also the discoverers of the technique of metal spinning, which was used to produce military helmets and dishes. The acme of pre-medieval metalcraft has got to be the Roman twin piston mine pump in the National Archaeological museum of Madrid. This wonderful machine was operated by two slaves to empty water from the vital silver mines of northern Spain which produced the coinage to pay the Imperial army. It is constructed of beautiful and complex bronze castings and resembles the pumps of the early industrial revolution. It is claimed that the pistons were lapped to fit, but I have not read any detailed technical reports of this artifact. It is probable that some of the wax patterns were turned, if not some of the finished castings. It lay undisturbed until recently, in the flooded mineshaft it was built to keep dry. • 在人们对小机床感到非常满意的时候，弓拉式车床被撑竿式车床所替代，这个发明可能是 凯尔特人和伊特鲁里亚人完成的，他们是欧洲第一批熟练车工。藉由在一个马镫或踏板上压迫下来，工作考虑和春天杆或在一些情形中，固定的弓被画下来。 脚的压力被释放导致工作快速地快速旋转而且允许车床工专注于操纵锐利的工具。塞尔特人用了车床转说和对于他们的出色二轮战车，碗，手镯轮轴, 腊为重要的演员阵容物体，软的金属和大部分模仿所有的,旋转磨石。 塞尔特人和罗马人也是金属制纺织的技术发现者,用来生产军事的钢盔和盘子。 前中古的 metalcraft 的顶点已经开始当蘼砣嗽诼淼吕锏墓铱脊叛Р┪锕葜猩セ钊业谋谩?这令人惊奇的机器被二个奴隶操作了倒空来自重要的银水生产了硬币铸造支付帝王的军队西班牙北部挖掘。 资讯科技被构造美丽的和合成物青铜铸件而且相似早的产业革命的泵。 资讯科技被宣称，活塞被重叠适合，但是我没有寥魏握庖桓鋈斯て返南晗讣际跎媳ǜ妗?资讯科技是可能的一些腊式样被转, 如果不是一些完成的铸件。 未受到干扰的俗人资讯科技直到最近,在它被建造保存干的被泛滥的 mineshaft 中。 Above: A German pole lathe of 1395. Two early examples of Spring Pole Lathes. The left-hand illustration is base don a Parisian manuscript dating from the mid-13th century. Scanned from Daumas' A History of Technology & Invention Vol. I.

10. The Pole Lathe（2） Of the Pole...The Pole is commonly made of a Fir-pole, and is longer, or shirter, or bigger or smaller, according to the weight of the Work the Workman designs to Turn : for the thicker the pole is, the harder must the tread be to be to bring it down; and for this reason, if the Pole prove too strong for their common or continued Work, they will weaken it by cutting away (with a draw knife) part of the substance off the upper and under side of the pole.The thick end of this Pole is nailed (or indeed rather pinned) up to some girder, or other Timber in the Ceiling of the Room, with a single Nail or Pin, that the Pole may move upon that Nail. -Joseph Moxon.Scanned from Country Furniture, by Aldren A Watson. On the String on a Spring-pole Lathe"Upon the thin end of the pole is ound a considerable bundle of string, that as a mandrel requires to be bigger than ordinary, or the wokr heavier, they may unwind so much if the string as will compass the mandrel twice, or (if the work be heavy) thrice; the easier to carry it about.This string is made of the guts of beasts (most commonly of sheep, and spun round of several thicknesses, of which the workman chuses such sizes as are aptest for his work; for large and heavy work, very thick, but for small and light work, thin..." -Joseph Moxon.

11. The Pole Lathe（3） 16th Century Turning ShopA turner working a making a sphere using a spring-pole lathe in a woodcut from Panoplia Omnium (1568), by Hartman Shopper. Scanned from M. Darlow's Woodturning Technicques

12. The Pole Lathe（4） A Metal Turning Lathe using a spring pole.Scanned from Moxon's Machanick Exercises"Brasiers that Turn Andirons, Pots Kettle, &c. have their Lathe made different from the Common Turners LAthe, as you may see in Plate 16. at A, where the Cheeks, Puppets and Rests, &c. are mujch stronger and the Pikes stronger and longer than those common Turners use... And as the common Turners work with a round string made of Gut, as hath been described... The Brasiers work with a Flat Leather Thong, which wrapping close and tight about the Rowler of their Mandrel, commands it the easier and more forcibly about... " Source: Joseph Moxon's Machanick Exercises. Moxon also goes on to describe how the tools have a double bend in them to brace them against the tool rest for more leverage, and that iron pegs in the tool rest provide additional support to the tool. One of my shop assistants working my foot-powered latheIn front of our booth at the Minnesota Renaissance Festival. It uses a bow instead of a spring pole. The metal bow was a spring that was scavenged from an antique baby buggy. I originally tied the cord directly to the bow string, but the bow was too stiff for me to work with for very long, so I added a pulley to the bow string following an example portayed in one of Roy Underhill's wood wright's books. "Some turners that work light work, such as cane-heads, ink-horns, &c. for which they need scarce remove the Puppets off their Lathe, use a common Bow, such as Archers use. The middle of this Bow the fasten over Head, with its string Horizontally downwards, and in the middle of of that String the fasten another String perpendicularly downwards, whose other end the fasten to the Treddle, and the String wound round their Work brings it around" -Joseph Moxon on using a bow for a spring. The Bed and framework is entirely pegged togther, the only screws are in the treadle where I cheated a little to repair it after the pegs started coming loose

13. clock-maker's screw-cutting lathe The Pole Lathe continued to be used almost unaltered from about 500 BC the the early part of this century. However, the inefficiency of its bi-directional action led to the development of continuous rotation lathes by the late middle ages, powered by assistants turning a large flywheel which transmitted the motion via rope bands to the work on the lathe. At the same time, the development of clocks spurred on mechanical invention. In 1364, complex planetary clocks were being constructed by hand, although mechanical dividing machines must have been used to cut the gearing involved. The worlds oldest surviving clock, installed at Salisbury in 1386 is notable for the complete absence of screw threads. The principle of the screw goes back to the time of Archimedes, where it was used to raise water. Screws in wood and metal were laboriously marked out and cut by hand using gouges or files. One of the first applications of the screw was for the wine and oil presses of the Romans, and later, for the cocking mechanism for powerful medieval crossbows. The illustration at left shows the state of play in 1480. The lead screw, on the right is cranked and advances through the headstock. The work, on the left, is fitted to a deep socket in the leadscrew and is free to rotate and advance through the tailstock as the crank is turned. The compound toolholder shown below is held in place anywhere along the slotted lathe bed by a wedge. The removable toolpiece is held in place by a screw, and can be advanced into the work on consecutive cuts by a screw mechanism. The thread cut on the work is necessarily the same as on the leadscrew, but is is conceivable that work of different diameters could be turned with the use of collets. German clock-maker's screw-cutting lathe c. 1480, showing (below) the tool-holder on cross slide.

14. These sketches by Leonardo da Vinci Leonardo da Vinci - a man of genius, and controversy. Artist, scientist, soldier, and cross-dresser(at least for arts sake). Most of the latest controversy hinges around exactly how original his mechanical ideas were. Was he the inventor of all the mechanical ideas that litter his copious manuscripts, did he draw ideas and mechanisms which were already in use, or did he use his genius to take other's ideas and improve them to a hitherto unachieved level of masterly design? The truth lies somewhere inside this scholarly Bermuda triangle. Certainly, it can be proven that some of his war machines, and even his famous diving suit were not original - ideas such as these had been illustrated in that overlooked masterpiece, "Belli fortis" by Konrad Kyeser, written in 1400. But if this is the case, where in hell did Leonardo see a copy of this rare manuscript from across the Alps? Or did he perhaps see the practical constructions of travelling German military engineers in action in Italy? Anyway, I am getting away from the point - go read one of the many excellent books or articles on Leonardo, it is lathes that concern us here. At left, you see two of Leonardo's designs from around 1500. The design for the plain turning lathe shows several important advances. The first is the substitution of continuous rotation for the back-and-forth motion of the pole lathe, the second is the flywheel, and the third is the adjustable tailstock. Supporting the flywheel between two bearings ensures greater power, rigidity, and accuracy, making it ideal for metal turning. The thread cutting machine uses two leadscrews on either side of the work, and appears to have two sets of change wheels below it, allowing three different pitched threads to be cut with the same machine. An overlooked feature of this machine is that using two lead screws would "average out" the inaccuracies, producing work which is more accurate that either original lead screw. Thus by producing several generations of leadscrew, accurate and consistent screw threads can be produced. And by producing different pitched lead screws with the original machine, an infinite proportional series of threads can be produced. Whether or not this machine was ever built, it shows true genius! Leonardo also drew a third lathe, substituting a longbow for the spring pole, but the details of the threading being carried out are unclear. It is said to show a hand cut thread on the work acting as a leadscrew for cutting the rest of the work progressively. Leonardo also drew a boring machine for use in making wooden pipes for water, or boring cannon with a unique self centering chuck to hold the stationary workpiece. Above: These sketches by Leonardo da Vinci show several remarkable innovations in machine design. The lathe at left has a treadle, a crankshaft and a large flywheel. The tailstock spindle can be adjusted by a hand crank. The device at right is a screw-cutting machine (not strictly a lathe), which has a set of change gears for cutting threads of various pitches.

15. The continuous-drive lathe This illustration shows a pewter working shop of the 16th century. The lathe is powered by continuous rotation from the "great wheel" in the background. The worker in the foreground is forming a sheet of pewter over a wooden former to produce a wine jug. The technique of metal spinning is thought to have been developed by the Celts and Romans, but evidence is sketchy. I picked this illustration because it is one of the earliest to show the "great wheel", but despite the primitiveness of this lathe, quite complex machinery was in use at this date. Torriano de Cremona, an Italian craftsman built a complex planetary clock for the emperor, Carlos V from 1540-43. It contained 1,800 gearwheels, which he cut using what has been described as a small lathe with a dividing attachment and rotary files to cut the teeth . Apparently, this machine was widely adopted by 1575. Above: The continuous-drive lathe of 1568 eliminated the back-and-forth rotation of the workpiece, produced by pole-and-treadle lathe, but required the services of a helper to turn a drive wheel.

16. Besson's drawing of a screw cutting lathe Besson's drawing of a screw cutting lathe shows a lack of solidity and rigidity that precludes its use for anything else than ornamental turning in wood and ivory. The Counter-Reformation and the growth of the baroque style lead to a wide scope of work for the ornamental turner, perhaps at the expense of the mechanician and scientist. Nonetheless, the growth of turning as a recreation for the upper classes and the continuing fascination with mechanical timekeeping kept progress in the lathe going over the next centuries, despite the stifling and sometimes brutal atmosphere of Counter-Reformation Europe. An interesting point in this picture is the conical workpiece. A machine working along similar principles but capable of machining metal would have been invaluable in the manufacture of woodscrews, which were laboriously handmade up till the 1780's. Above: A lathe designed by Jacques Besson, Leonardo's successor as engineer to the French court, incorporated a clever means for feeding the cutting tool longitudinally in coordination with the rotation of the workpiece (Workpiece is the tapered screw being cut at the left). The coordination of tool feed and workpiece rotation is maintained by pulleys.

17. The bow driven lathe The lathe of 1671 portrayed at left comes from a work on optics by Father Cherubin d'Orleans. It is not generally appreciated that the curved mirrors so fashionable in this era, as well as lenses for glasses and scientific equipment were ground on lathes such as this. Cherubin was particularly concerned with reducing friction, accurate bearings and adjustable speeds, as this ingenious lathe shows. Above: This lathe of 1671 was remarkably advanced for its time. The bow drive was powered by an apprentice who placed his foot in a stirrup and pumped. The crankshaft was turned by the combined action of foot and bow. A large flywheel kept the piece turning smoothly. The lathe, described by Cherubin d'Orleans, used pulleys of various sizes to provide various speeds of revolution.

18. a turners workshop specialising in screw-making This illustration is from Diderot's famed Encyclopedia, published from the 1740s onwards. It shows a turners workshop specialising in screw-making. The first close-up shows a screw-cutting lathe that is pole operated, in the time-honoured style, but the "great wheel" in the background and pulley behind the box-chuck shows an alternate method of propulsion. The box on the right contains a number of sliding keys which engage with threads of different pitches cut on the lathe spindle, in this case three. The lathe is massively built, and the turner appears to be cutting a screw for a wine, olive or possibly a printing press. The light weight tool rest indicates the material being worked is wood.

19. Despite the suggestion by Rolt that the lathe in plate 3 was a theoretical exercise that was never built, here we appear to have its working descendent. The only point of doubt is the leadscrew operated toolholder. The steady rest, however, appears to be on the wrong side of the collet attaching the work to the leadscrew. This machine is simple, yet efficient. However, unlike Leonardo's machine, it cannot improve the accuracy of its own leadscrew. At this point it should be mentioned how these master screws were made. Straight lines corresponding to the desired pitch were drawn on a sheet of paper which was wrapped and glued onto the centered and trued blank. The threads were carefully cut by hand with triangular files. Later, in the 18th century, the screw was turned with a thread chasing tool to get a consistent finish and register down the whole length, then reversed end to end and turned again. It shouldn't be forgotten that once a reasonable master was cut, it could be reproduced in bronze by casting, rather than by machining from scratch. While the principle of the tap and die had been understood by the ancients, it is uncertain when these useful tools were first put into general use.

20. Father Charles Plumier, writing in 1701 was particularly concerned with applying the advances in ornamental turning to practical turning in metals. This illustration shows the heavy duty machine he constructed for turning iron and the series of three pictures show the process of constructing an accurate,thread cutting lathe for use with metal. First a wooden model of the lathe spindle was made, and the iron forged to shape. The rough spindle was centered and turned with the L-shaped lathe tool between centres, with a shelf on the tool rest providing support for the heavy stresses of machining iron. The work was rotated by direct drive by a cord looped around it. Above: Turning an iron mandrel on a lathe between poppets. The mandrel is rotated by means of a cord looped round it which is attached to a foot-treadle and a pole.

21. The caption of this picture is self-explanatory. The thread used would have been generated as detailed above and would have been a selected section which was the most consistent of a longer thread. Above: Cutting the screw on the mandrel with the tool C, which is fixed by the pins in the block M. A guide-screw soldered into the end of the mandrel works in a female thread in the poppet K; thus the accuracy of the screw on the mandrel itself depends on the accuracy of the guide-screw.

22. The finished lathe headstock, showing the keys which engage the different pitch threads on the lathe spindle. When engaged, the spindle advances through the headstock taking the work with it, and allowing the workpiece to be cut with a short section of thread. The same lathe can also be used for plain turning. Two styles of mandrel are shown at bottom. This type of lathe was in general use for about the next 150 years for cutting threads on metal, as well as ornamental work. Above: The mandrel lathe complete. The traversing-screw on the mandrel engages in the left-hand poppet, so that it travels to and fro when rotated fast in one direction and then in the other by a cord looped around at B. The cord is connected at one end to a treadle and by the other to a pole. D is the tool-rest. The frames of all these lathes were of wood. When continuous rotation was required, a plain mandrel was used on which a pulley was mounted. An endless cord passed round this pulley and a large wheel turned by a crank. Underneath are two forms of mandrel with traversing-screws. Note short thread at the other end for attaching the work.

23. This illustration has side and top views of the keyed headstock, as well as a general illustration of a treadle lathe based on the same principle, albeit of a later date. Above: Keyed headstock for threading on a lathe. Diagram of a mandrel with threads of various pitches, and its mounting on the lathe (from Plumier's "L'art de Tourner" and Holtzapffel's "Turning and Mechanical Manipulation" 1847).

24. This picture shows the sophisticated nature of compound tool holders in use during the mid 18th century for ornamental turning. This one is from the Encyclopedia of Diderot. A rare accessory between 1480 and 1650, it then became very popular. Above: Pivoting toolholder of a guilloching lathe.

25. Clockmaker's lathe This deceptively simple lathe, or "turns" could be powered by hand held bow, spring pole, treadle, Above: Clockmaker's lathe. or falling weights. This one dates from the period 1650-1700, but similar ones were used until recently with hardly any modification. Its advantage is its all-metal construction, and the accurate square bed. To use it, it was clamped in a vice at the workbench. Because of the small size of the work, even hardened steel could be cut using a razor sharp steel graver. Above: Clockmaker's lathe.

26. Division plate mounted on a clockmaker's lathe This picture shows a similar lathe from about a hundred years later, with hardly any change apart from the introduction of more complex accessories. The accuracy and form of construction of these small lathes was quickly to influence the construction of larger machines. Around 1710, Polhem in Sweden constructed several lathes with all-metal construction, geared drive and leadscrew to machine accurate rollers for rolling steel bars. The machines were a closely guarded secret, as was Polhem's cylindrical grinder, but in a manuscript, its construction is briefly described. These lathes were notable for the extensive use of metal in the construction. There was however, no improvement over the methods of generating screw threads by hand outlined above in constructing the iron leadscrews for Polhem's lathes. A master was cut in hardwood by hand, attached to an iron blank and and the final thread generated by many light cuts, a follower transmitting motion from the master to the tool slide. However, as in Besson's lathe, it was the tool holder which moved longitudinally, not the work, producing more accurate results than the traversing mandrel. Absolute accuracy of form was not necessary for the thread, as the final machines were only used for plain turning as far as we know. These machines were driven by water power, which, with animal and wind power was gaining popularity for large turning work where it was available. Above: Division plate mounted on a clockmaker's lathe. The plate has only a single divided circle.

27. Thiout's lathe for cutting screw-heads This shows the thread cutting lathe developed for horological work by Antoine Thiout in around 1741. The lead screw is supported between the two members of the headstock, and advances a nut as it is cranked, while also rotating the work by means of a bell chuck. Motion from the nut is transmitted by a series of linkages to the toolholder which cuts the thread upon the rotating work. The beauty of Thiout's machine is that the linkages are adjustable to a number of pitches by a system of pegs and index holes. So again, for the first time since Leonardo, we have a machine which is able to improve upon the metrical accuracy of the pitch on its own leadscrew. Thiout's linkage proved to be very important to subsequent machine builders. The elegant all-metal construction makes for a fascinating and accurate machine. Above: Thiout's lathe for cutting screw-heads on spindles for clocks and watches.

28. Improved automatic fusee engine This is a fully automatic fusee engine developed by Berthoud in 1763. A fusee is a hyperbolic conical grooved component (marked "F" in the drawing) used to regulate the power produced by a clock spring. Like Besson's ornamental lathe, the tool follows the surface of the work, but using a template instead of weights. An adjustable inclined plane is pulled past the toolrest advancing it to generate the thread to whatever pitch required. Okay, so I am straying a bit from the lathes we all know and love, but I wanted to demonstrate the complexity and ingeniousness of the tools available to early instrument makers. Above: Improved automatic fusee engine by Ferdinand Berthoud, 1763.

29. Ramsden's threading lathe Foremost amongst instrument makers in England was the remarkable Jesse Ramsden (1735-1800). He was a maker of mathematical and astronomical instruments which required threads of fine pitch and great accuracy, and to that end, constructed a series of lathes with the most painstaking of care, each one enabling him to construct a more accurate successor. The first picture at left represents his first lathe. The crank turns the workpiece directly, and the leadscrew through a series of change-gears. The leadscrew drives the toolholder along a triangular iron bed and the diamond tool can thus cut a variety of threads. This is the same basic system on which the familiar amateur's lathe operates today. Above: Ramsden's threading lathe. The object to be threaded can be seen in the upper portion. The tool that attacks it has a diamond tip which can cut tempered steel. This tool is held by a carriage with a collar, pulled by the lead screw in the lower portion of the drawing.

30. This is Ramsden's final lathe. The tool-slide is attached to the hub of a large geared wheel by a thin steel strip which pulls it along as the large gearwheel rotates. As the handle is cranked, the work is rotated by a helical gear meshing with a series of variable change-gears. At the same time, the large gearwheel is rotated by a short thread cut as accurately as possible to a pitch of 20 threads per inch (tpi), thus advancing the tool slide. With this machine, Ramsden was able to cut threads as fine as 125 tpi and of any length to an extreme level of accuracy. Above: Precision screw-cutting lathe by Jesse Ramsden, 1778.

31. Vaucanson's lathe One of the main problems with the "cult of the inventor" I mentioned in my introduction is that, as in all mythologies, it is the winners who write the story, while their competitors are relegated to roles as helpers, villains, or, worse still, written out of the story entirely. Such is the case with the history of the industrial revolution. England was the winner of the first round of the industrial revolution, due to a fortuitous set of factors, only one of which was the inventiveness and creativity of its scientists and technicians. England's competitors, and in particular their political and military rivals have suffered until recently from the strong Anglo-centric bias of industrial historians. The progress of the lathe in England owes much to the innovations introduced by the Verbruggens at Woolich arsenal in the 1760's. (By the way, please don't rely on Rolt's section on cannon boring, it is the only bad part of an excellent book). The Verbruggens in their turn had been influenced by the work of Maritz at Geneva in 1715 and more particularly at Strasbourg in the 1730's. The Encyclopedia of Diderot should be enough to show the advanced state of industry in France at mid-century, but the illustration at left shows us concretely that France held the lead in European technology before it was surpassed by England. This lathe was built by Jacques de Vaucanson in 1751. It is a single purpose machine, probably built to turn iron rollers a metre long and a maximum of 30 cm in diameter. The supporting frame is made of bolted iron bars, and the bed borrows from horological practice in having an diamond shaped section to resist thrust and shed swarf. The bronze tool slide is advanced by hand operated leadscrew. How similar this is to Polhem's lathes of 1715, we can only speculate. Above: Vaucanson's lathe, c. 1775.

32. Senot's lathe This remarkable machine, constructed by Senot in 1795 has all the features we associate with modern lathes - adjustable chuck, tailstock, steadies, travelling steady, bearings, leadscrew and change-gears. In 1798 David Wilkinson of the USA was building a machine with similar, but less sophisticated features. By 1806 he was producing a general purpose lathe, but despite its popularity, examples are unknown today. Above: Senot's lathe, 1795.

33. Henry Maudslay's first screw-cutting lathe Henry Maudslay was no doubt a talented thinker and machinist,but by this point, I hope it is clear that his deification as the inventor of the modern lathe is a fiction. The illustration at left shows the lathe he built after setting up business for himself in 1797. It has the familiar prismatic bed, or rather beds, with a leadscrew between them. There is evidence that the leadscrew was designed to be interchangeable, not only to allow different pitches of thread to be cut, but also to allow a hand-cut master thread to be used to generate a more robust and accurate replacement leadscrew. The lathe was later fitted with change-gears to allow changes of pitch. The cross slide is graduated, and the saddle has a split nut to engage and disengage it. Like Ramsden before him, Maudslay went to infinite pains to obtain accurate threads for leadscrews. He tried all known methods and finally settled on the inclined knife. The knife was mounted on a prismatic guideway on a swivelling toolholder. The oblique incision made by the knife in soft metal or wood carried it along the blank cylinder of the work as it was rotated, and by adjusting the inclination of the tool, a groove of any pitch could be cut. Using this groove as a basis, the thread was then cut by hand. Above: Henry Maudslay's first screw-cutting lathe, c. 1800.

34. Maudslay's second screw-cutting lathe Maudslay's second great contribution was the appreciation that in the quest for precision, true plane surfaces are almost as important as accurate screw threads. He introduced the use of surface plates and hand scraping. These techniques were put to use in building his second lathe,a flat bed model, illustrated here. This solid, well designed machine was built in 1800, and was followed by a micrometer in 1805. The first lathe was used to cut the permanently mounted leadscrew of the second, which was equipped with 28 change wheel and a travelling steady. In his third lathe, he combined prismatic and flat guideways, and stepped drive pulleys. He was able to machine a brass screw 7 feet long with an error in length of only 1/16 from the computed length. Still not satisfied, he devised a linkage like that of Thiout to correct this slight error, producing an accurate thread 5 feet long with a pitch of 50 tpi which was used to calibrate astronomical instruments. Threads like these made possible Maudslay's micrometer, nicknamed 'the Lord Chancellor", reputedly accurate to 1/10000 of an inch. Above: Maudslay's second screw-cutting lathe, c. 1800.

35. Maudslay had almost all the great names in English engineering pass through his workshop as trainees in the early years of the 19th century. These interesting people's lives and labours are covered in great detail already in many publications, but I thought I would round off this little essay with an illustration of a typical treadle lathe of the late 19th century which was the product they were responsible for developing. Machines like this were made until the great depression, and can still be found in use today by dedicated masochists everywhere.

36. REFERENCES L.T.C Rolt,"Tools for the Job", Batsford, 1965 R.S.Woodbury, "The Origins of the Lathe" in Scientific American, April 1963Dennis Diderot, "Illustrations from the Encyclopedia", Dover Art Books, 1982 Tubal Cain, "Workholding in the Lathe", Argus, 1987Maurice Daumas ed.,"A History of Technology and Invention", New York, 1969 particularly Vol.2, Ch.12 by Daumas and Garanger; Vol. 3, Part 2, ch.2 by Garanger Singer, Holmyard, Hall, Williams eds.,"History of Technology", Oxford, 1956 particularly Vol. 4, Ch.13 "Precision Mechanics" by Daumas; Vol.4, Ch.14 "Machine Tools" by Gilbert.

37. a